A critical vulnerability in PuTTY has prompted developers to release an urgent update to address the potential recovery of secret keys. PuTTY, a widely-used open-source client for SSH, Telnet, and other network protocols, was found to generate heavily biased ECDSA nonces in the case of NIST P-521, facilitating full secret key recovery. This vulnerability, identified as CVE-2024-31497, poses significant security risks, as malicious actors could exploit it after seeing roughly 60 valid ECDSA signatures generated by any PuTTY component under the same key.
Researchers from Ruhr University Bochum in Germany discovered the flaw, emphasizing that compromised NIST P-521 client keys used with PuTTY should be treated as compromised even after patching, due to the potential retrieval of signatures by adversaries. PuTTY developers have provided insights into how threat actors could exploit the vulnerability, highlighting the risk of unauthorized access to servers and the potential for supply chain attacks. Versions 0.68 through 0.80 of PuTTY are affected, with version 0.81 released to address the vulnerability, urging immediate revocation of affected keys to mitigate risks.
Moreover, the ramifications extend beyond PuTTY, as several products relying on affected versions of PuTTY, including FileZilla, WinSCP, TortoiseGit, and TortoiseSVN, are also vulnerable. Patches or mitigations are available for these products as well. With the National Vulnerability Database warning of potential supply chain attacks, the urgency of addressing this vulnerability cannot be overstated, prompting users to update to PuTTY version 0.81 and revoke affected keys promptly to safeguard against potential exploits.
